Conventional computer systems, including mainframes, mini-computers and desktop computers, use a variety of means for cooling the integrated circuits (IC's) that they contain. Desktop computers, for example, typically employ a small fan that blows air across the motherboard of the computer. Heat sinks are often affixed to the integrated circuits to facilitate heat dissipation.
Mainframe computers typically employ more sophisticated cooling systems. For example, U.S. Pat. No. 4,674,004, describes a system of parallel cooling for use in a mainframe computer wherein each circuit of the mainframe receives its own supply of ambient-temperature air. This type of forced-air cooling permits the use of very small heat sinks in relation to the amount of power that is being dissipated by the various circuits. Mainframe computers have also traditionally been housed in air-conditioned computer rooms that provide a well-controlled, cool air environment.
As computer systems continue to downsize, the cooling environments for circuit boards become more demanding. The trend is to move computer systems out of isolated computer rooms into open office areas. This causes two problems. First, the cooling air provided for the system is not as well-controlled and is usually hotter than that found in an air-conditioned computer room. Second, because of the noise associated with cooling fans, smaller fans are often used with correspondingly reduced airflow.
New systems must be designed to deal with these less friendly thermal conditions, and one solution has been to employ larger, more efficient heat sinks. Larger heat sinks with greater surface area and better conduction paths are able to cool the integrated circuits of a computer system, despite the harsher thermal conditions.
A problem arises, however, when the designer of a computer system intended for harsher environments wants to incorporate an existing circuit board that was originally designed for use in a more controlled computer room environment. The heat sinks provided on such circuit boards are often insufficient to adequately dissipate heat in the harsher environment of the new system. Accordingly, there is a need for an apparatus that allows the heat sink capabilities of an existing circuit board to be upgraded for use in newer, more demanding thermal environments, thus avoiding the need to redesign the entire circuit board. The present invention satisfies this need.